Assuming the signal has been well-isolated, design a two-stage circuit to indicate heartbeat from an EKG signal. The first stage should amplify the biosignal to a 1V range (defined from Q-R), and the second will indicate heartbeat using a comparator. Assume the detection will occur using the R-wave of the signal. Describe how the output from the second stage indicates a heartbeat. Describe a possible third stage to provide an audible output indicating the heartbeat.